Journal of the British Interplanetary Society VOLUME 72 NO.5 MAY 2019 General issue A REACTION DRIVE Powered by External Dynamic Pressure Jeffrey K. Greason DOCKING WITH ROTATING SPACE SYSTEMS Mark Hempsell MARTIAN DUST: the Formation, Composition, Toxicology, Astronaut Exposure Health Risks and Measures to Mitigate Exposure John Cain THE CONCEPT OF A LOW COST SPACE MISSION to Measure “Big G” Roger Longstaff www.bis-space.com ISSN 0007-084X PUBLICATION DATE: 26 JULY 2019 Submitting papers International Advisory Board to JBIS JBIS welcomes the submission of technical Rachel Armstrong, Newcastle University, UK papers for publication dealing with technical Peter Bainum, Howard University, USA reviews, research, technology and engineering in astronautics and related fields. Stephen Baxter, Science & Science Fiction Writer, UK James Benford, Microwave Sciences, California, USA Text should be: James Biggs, The University of Strathclyde, UK ■ As concise as the content allows – typically 5,000 to 6,000 words. Shorter papers (Technical Notes) Anu Bowman, Foundation for Enterprise Development, California, USA will also be considered; longer papers will only Gerald Cleaver, Baylor University, USA be considered in exceptional circumstances – for Charles Cockell, University of Edinburgh, UK example, in the case of a major subject review. Ian A. Crawford, Birkbeck College London, UK ■ Source references should be inserted in the text in square brackets – [1] – and then listed at the Adam Crowl, Icarus Interstellar, Australia end of the paper. Eric W. Davis, Institute for Advanced Studies at Austin, USA ■ Illustration references should be cited in Kathryn Denning, York University, Toronto, Canada numerical order in the text; those not cited in the Martyn Fogg, Probability Research Group, UK text risk omission. Raghavan Gopalaswami, Aerospace Researcher, India ■ Captions must be labelled with their Fig. number and should be as short as possible. Lamartine Guimarães, Institute for Advanced Studies, Brazil Mark Hempsell, Hempsell Astronautics Ltd, UK Illustrations should be: Takuto Ishimatsu, Massachusetts Institute of Technology, USA ■ Colour or mono, but should be as close to print Les Johnson, Marshall Space Flight Center, USA resolution (300 dpi) as possible. Poor-quality illustrations may compromise the acceptance of Terry Kammash, University of Michigan, USA paper for publication. Images embedded in Word Kelvin F. Long, Initiative for Interstellar Studies documents may be acceptable, but JBIS reserves Inoue Makoto, Institute of Astronomy & Astrophysics Academia Sinica, Taiwan the right to request separate higher-resolution Gregory L. Matloff, City University New York, USA image files from the author prior to publication. Koichi Mori, Nagoya University, Japan ■ Responsibility for copyright clearance of images rests entirely with the author. Richard Obousy, Richard Obousy Consulting LLC, USA Robert Parkinson, BIS, Aylesbury, UK Submission of papers George Schmidt, NASA John H Glenn Research Center, Ohio, USA ■ Papers for consideration should be sent by Paul Schuch, The SETI League Inc, USA email to [email protected] as both a Word document and as a Word PDF file (in order to Tabitha Smith, Bifrost, USA check for font anomalies), together with any Andreas Tziolas, Variance Dynamical Corporation, USA separate image files. Chris Welch, The International Space University, Strasbourg, France ■ If a paper is accepted for publication, the Friedwardt Winterberg, University of Nevada, Reno, USA author will be asked to sign a License to Publish form. This can be downloaded at www.bis- space.com/wp-content/uploads/2012/08/ WebsiteLicense.pdf. ■ Authors will receive a complimentary copy of the issue in which their paper appears. Editor Roger Longstaff Deputy Editor Duncan Law-Green Associate Editors Stephen Ashworth, We respectfully ask authors to adhere to these Keith Cooper, Stephen Gamble, Paul Gilster, Rob Swinney, Production MP3 Media guidelines. Failure to do so will result in the Promotion Gill Norman JBIS Office British Interplanetary Society, Arthur C. Clarke House, delay of acceptable papers for publication. 27-29 South Lambeth Road, London, SW8 1SZ, United Kingdom tel +44 (0)20 7735 3160 email [email protected] www.bis-space.com Our full Guidelines for Authors can be downloaded DISTRIBUTION from www.bis-space.com JBIS is distributed worldwide by mail and may be received by annual subscription or purchase of single copies. It is available through membership of the British Interplanetary Society at much reduced rates. Subscription details for members, non-members and libraries are available from the above address. JBIS is a publication that promotes the mission of the British Interplanetary Society. Opinions expressed in signed articles are those of the contributors and do not necessarily reflect the views of the Editor or the Council of the British Interplanetary Society. Security clearance, where necessary, is the responsibility of the author. Published by the British Interplanetary Society. Registered Company No: 402498. Registered Charity No: 250556. Printed by Latimer Trend & Company Ltd, Estover Road, Plymouth, PL6 7PY, England. © 2018 British Interplanetary Society. No part of this magazine may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying or recording by any information storage or retrieval system without prior permission from the Publishers. CONTENTS VOLUME 72 NO.5 MAY 2019 146 A REACTION DRIVE Powered by External Dynamic Pressure Jeffrey K. Greason 153 DOCKING WITH ROTATING SPACE SYSTEMS Mark Hempsell 161 MARTIAN DUST: the Formation, Composition, Toxicology, Astronaut Exposure Health Risks and Measures to Mitigate Exposure John Cain 172 THE CONCEPT OF A LOW COST SPACE MISSION to Measure “Big G” Roger Longstaff OUR MISSION STATEMENT The British Interplanetary Society promotes the exploration and use of space for the benefit of humanity, connecting people to create, educate and inspire, and advance knowledge in all aspects of astronautics. JBIS Vol 72 No.5 May 2019 145 JBIS VOLUME 71 2018 PAGES 146–152 A REACTION DRIVE Powered by External Dynamic Pressure JEFFREY K. GREASON, Electric Sky, Inc., 602 North Baird St., Suite 200, Midland, TX, 79701, USA email [email protected] A new class of reaction drive is discussed, in which reaction mass is expelled from a vehicle using power extracted from the relative motion of the vehicle and the surrounding medium, such as the solar wind. The physics of this type of drive are reviewed and shown to permit high velocity changes with modest mass ratio while conserving energy and momentum according to well-established physical principles. A comparison to past propulsion methods and propulsion classification studies suggests new mission possibilities for this type of drive. An example of how this principle might be embodied in hardware suggests accelerations sufficient for outer solar system missions, with shorter trip times and lower mass ratios than chemical rockets. Keywords: Propulsion, Reaction drive, Solar wind, External power, Dynamic pressure 1 INTRODUCTION NOMENCLATURE In the sixty years since the first interplanetary spacecraft (Luna drag on the ship, in the ship frame (negative if it 1), scientific probes have been flown to all the large bodies in the decreases a positive velocity), N solar system, and, after decades of flight time, the twin Voyager specific impulse, m/s 1 and 2 spacecraft are entering the boundary between the solar power, (positive if supplied from ship, negative if system and interstellar space. However, missions to the outer supplied to the ship), W solar system are still very difficult, with long trip times, even thrust applied to ship (positive if it increases a with use of gravity assist maneuvers. positive velocity), N net thrust of the ship, surplus of thrust over drag, Substantial reductions in trip times to the outer solar sys- tem or for interstellar precursor missions are difficult for fun- N damental physical reasons. Fast trips imply high velocities: a reaction mass expelled, kg constant speed of 100 km/s is only ~20 AU/year, beyond any mass of the ship, kg demonstrated capability (though achievable with a close-solar mass of the surrounding medium which interacts flyby Oberth maneuver). Fast trips also imply that accelera- with the ship, kg tion cannot be too small: a 29 AU trip (Neptune from Earth) dynamic pressure of the medium on the ship, Pa of 100km/s peak velocity requires a constant acceleration of at velocity of the ship in the rest frame, m/s 2 least 0.005 m/s to achieve a two-year flight time (ignoring So- velocity of the surrounding medium in the rest lar gravity), otherwise too much time is spent in acceleration frame, m/s and braking to take advantage of high speed. before interaction with the propulsion system, in the rest frame, m/s With rocket propulsion, high velocity implies either high mass ratio (expense) or high exhaust velocity (high specific en- after interaction with the propulsion system, ergy of the propellant). High acceleration implies high specific in the rest frame, m/s power, which is why electric rockets have not been able to over- exhaust velocity of the reaction mass, relative to come these limitations. Nuclear propulsion systems offer high the ship, in the ship frame, m/s specific energy, but whether they can combine high specific freestream velocity; velocity of the surrounding energy with high specific power remains to be demonstrated. medium